模拟干湿循环及低应力条件的膨胀土抗剪强度试验研究

发布时间：2018-03-13 05:24

本文选题：膨胀土边坡　切入点：干湿循环　出处：《长沙理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：大气干湿循环作用下膨胀土边坡破坏多呈浅层性,穿越膨胀土分布区新建公路经历一个雨季后挖方边坡常连片滑坍,造成巨大工程、经济损失并带来沿线严重生态环境破坏甚至水土流失。研究并获得这种浅层破坏规律、提出有效的工程处治方法既十分迫切又特别重要。对此,本文依托国家自科基金和南宁外环膨胀土路基处治两项目,开展模拟干湿循环及低应力条件的膨胀土抗剪强度试验研究。首先,通过分析膨胀土边坡浅层坍滑破坏的外部原因,认定必须改变常规试验方法以真实模拟边坡破坏的低应力条件及经历的干湿循环过程,提出改进剪切试验设计及施测方法,自制了配套小型制样仪并论证实施慢剪的试验方案。按设定方案在直剪仪上系统开展南宁外环膨胀土慢剪试验,获得干湿循环下原状、重塑样的系列测试结果,论证了含低应力条件的合理性以及分高、低应力段定强度指标反映膨胀土强度非线性特点的必要性；还研究了干湿循环效应对膨胀土强度衰减的影响,验证了新试验法的合理有效性。为进一步检验新法试验的普遍合理性,取百色、北京西六环膨胀土做相同试验,分析对比三土样测试数据,结果表明：干湿循环效应对各种膨胀土的影响相近,抗剪强度均宜分段表达；相同条件下三土样测得的最终强度值均降至同一区间；c值随循环次数衰减呈指数函数变化,而φ值降幅不显著；还探讨了膨胀土强度衰减的基本原因。最后,将实测参数带入FLAC2D模型开展南宁外环一膨胀土坡数值模拟,得到浅层破坏结果与实际相符；此外还用灰色关联度法分析了影响c值衰减的因素排序。研究结论对分析膨胀土边坡的稳定性有重要参考价值。
[Abstract]:The damage of expansive soil slope under the action of dry and wet circulation in the atmosphere is mostly shallow. After a rainy season, the excavated slope often slides and collapses through the newly built highway in the expansive soil distribution area, which results in a huge project. Economic loss and serious ecological environment damage and even soil and water loss along the route. It is very urgent and especially important to study and obtain this shallow damage law and put forward effective engineering treatment methods. In this paper, based on the two projects of National Self-science Foundation and Nanning Extra-ring expansive soil subgrade treatment, the shear strength of expansive soil under simulated dry and wet cycles and low stress conditions is studied. Firstly, the external causes of shallow collapse failure of expansive soil slope are analyzed. It is concluded that it is necessary to change the conventional test method to simulate the low stress condition of slope failure and the dry and wet cycle process, and the improved shear test design and test method are put forward. A series of test results of undisturbed and remolded samples under dry and wet cycles were obtained by self-made small scale samplers and demonstration of the test scheme of slow shear, which was carried out systematically on the direct shear apparatus in Nanning outer ring under dry and wet cycles. The reasonableness of the condition with low stress and the necessity of reflecting the nonlinear characteristics of strength of expansive soil with the constant strength index of high stress and low stress are demonstrated, and the influence of dry-wet cycle effect on strength attenuation of expansive soil is also studied. The reasonable validity of the new test method has been verified. In order to further test the universal rationality of the new test, Baise, Beijing West sixth Ring expansive soil is used to do the same test, and the test data of three soil samples are analyzed and compared. The results show that the effect of dry-wet cycle on various expansive soils is similar, and the shear strength should be expressed in sections, and the final strength values of the three soil samples are reduced to the same interval, and the values of c decrease with the number of cycles. The decrease of 蠁 value is not significant, the basic reason of strength attenuation of expansive soil is also discussed. Finally, the measured parameters are introduced into the FLAC2D model to simulate the slope of the expansive soil around the outer ring of Nanning, and the results of shallow failure are in agreement with the actual situation. In addition, the grey correlation degree method is used to analyze the order of factors affecting the attenuation of c value, and the results are of great reference value to the analysis of the stability of expansive soil slope.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U412.221

【共引文献】